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September 07, 2012
NRC issues post-Fukushima guidance

The Nuclear Regulatory Commission (NRC) has released three interim staff guidance (ISG) documents that nuclear power plant operators may use to meet the requirements of safety-related orders the NRC issued to reflect lessons learned from Japan’s Fukushima Daiichi nuclear accident.
               According to the NRC, the ISGs represent acceptable approaches to meeting the orders’ requirements before their December 31, 2016, compliance deadline.  Adherence to the ISGs is not mandatory, but plant operators would need NRC approval if they want to follow a different compliance approach.  The NRC issued draft versions of the ISGs in May 2012 and asked for public input.  The final ISGs reflect information gained from the month-long comment period and subsequent public meetings, says the NRC.
Equipment, containment, monitoring

    • The first order (accession number ML12229A174; industry document accession number ML12242A378) requires all U.S. plants to better protect portable safety equipment put in place after the 9/11 terrorist attacks and to obtain equipment sufficient to simultaneously support all reactors and spent fuel pools at a given site.  The ISG for this order endorses the industry’s updated guidance for dealing with a scenario that knocks out all of a plant’s alternating current electric sources.  The updated approach includes the use of backup power supplies for devices that would burn off accident-generated hydrogen before it could accumulate to explosive levels.
    • The second order (accession number ML12229A475) applies only to U.S. boiling-water reactors that have Mark I or Mark II containment designs.  Mark I reactors must improve installed venting systems that help prevent core damage in the event of an accident.  Mark II reactors must install these venting systems. The ISG for this order provides more detailed technical information on the vents as well as how vent designs and operating procedures should avoid, where possible, the reliance on plant personnel taking actions under hazardous conditions.  Containment in the Fukushima Daiichi plant followed the Mark I design.
    • The third order (accession number ML12221A339; industry document accession number ML12240A304) requires all plants to install enhanced equipment for monitoring water levels in each plant’s spent fuel pool.  The ISG for this order largely endorses an industry document that NRC staff concludes will successfully implement the order.  The ISG defines in more detail the water levels the new equipment must accurately report, as well as standards for equipment mounting, powering and testing, personnel training, and other criteria.  The final ISG notes several areas, including instrument qualifications and instrument protection from falling debris, where the industry revised its initial approach. An exception in the staff’s endorsement sets specific seismic criteria to ensure the instruments will survive an earthquake.

Available on ADAMS
               Each of the ISGs and the industry documents on the first and third guidance are available in the NRC’s electronic document database (http://adams.nrc.gov/wba).  They can be obtained by performing a content search with the above accession numbers.

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